BMR Calculator: Your Body's Engine
Discover your metabolic baseline. Learn exactly how many calories you burn just by staying alive—before you even get out of bed.
Your Details
Basal Metabolic Rate
Calories / Day (Resting)
Your Basal Metabolic Rate (BMR) is the number of calories your body requires for basic life-sustaining functions: breathing, circulation, cell production, and nutrient processing.
Most people think exercise burns the most calories. In reality, 60-75% of your daily energy is burned by your BMR. You burn more calories sleeping and thinking than you do on the treadmill.
BMR vs. TDEE: The Vital Difference
BMR is your "Coma Calories"—energy needed if you never moved. TDEE (Total Daily Energy Expenditure) is the number you actually care about.
- • Brain function (~20% of BMR)
- • Liver function
- • Heart beating
- • Breathing
- • BMR (The Foundation)
- • NEAT (Fidgeting, Standing)
- • EAT (Exercise Activity)
- • TEF (Digesting Food)
To lose weight, you must eat below your TDEE, but ideally above your BMR.
Hacking Your Metabolism
The High-Octane Fuel Strategy
You can't change your age, but you can change your tissue. Muscle is metabolically expensive—it burns 3x more calories at rest than fat does.
- Strength Training:The only reliable way to increase BMR long-term. Lifting weights sends a signal to your body to burn more energy 24/7 to repair and maintain muscle fibers.
- Protein Intake:Protein has a high Thermic Effect (TEF). Your body burns 20-30% of the protein calories just trying to digest them. (Carbs are only 5-10%).
The Math: Mifflin-St Jeor Equation
This is considered the "Gold Standard" for BMR accuracy (Study: J Am Diet Assoc 2005). It calculates the energy cost of maintaining your body's mass.
*Weight in kg, Height in cm, Age in years.
Calculation Example
Profile: 30-year-old Woman, 165cm, 65kg.
- Weight Term: 10 × 65 = 650
- Height Term: 6.25 × 165 = 1031.25
- Age Term: 5 × 30 = 150
- BMR: 650 + 1031.25 - 150 - 161 = 1,370 cal/day
Takeaway: She burns 1,370 calories just existing. If she walks around and works (Sedentary x 1.2), her real maintenance is ~1,644 calories.
The Activity Factor
How your TDEE (Real Burn) creates a deficit, using a BMR of 1,500.
Desk Job
BMR: 1,500
Multiplier: x1.2
Weight loss calories: ~1,300
Gym 3x/Week
BMR: 1,500
Multiplier: x1.55
Weight loss calories: ~1,825
Labor Job
BMR: 1,500
Multiplier: x1.9
Weight loss calories: ~2,350
Standard Activity Multipliers
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | x 1.2 | Desk job, little to no exercise. |
| Lightly Active | x 1.375 | Light exercise 1-3 days/week. |
| Moderately Active | x 1.55 | Moderate exercise 3-5 days/week. |
| Very Active | x 1.725 | Hard exercise 6-7 days/week. |
| Extra Active | x 1.9 | Physical job + hard exercise training. |
Related Tools
Is it true that eating late slows metabolism?
No. Your metabolism runs 24/7, even while you sleep. The total amount of calories matters far more than the timing. However, late-night eating is often linked to weight gain because people tend to choose calorie-dense snacks when tired.
Why is my friend eating more than me but staying thin?
They likely have a higher NEAT (Non-Exercise Activity Thermogenesis). They might fidget more, pace while talking, or have an active job. NEAT can burn up to 800 extra calories a day without 'working out'.
Does drinking cold water boost metabolism?
Technically yes, but the effect is negligible (about 8 calories per glass). You would need to drink ice water all day to burn off a single cookie. Focus on muscle mass instead.
What is 'Starvation Mode'?
If you cut calories too aggressively (below your BMR) for a long time, your body adapts by slowing down non-essential functions to correct the energy deficit. This 'adaptive thermogenesis' makes further weight loss very difficult.
How does aging affect BMR?
Metabolism slows by about 1-2% per decade after age 20. However, most of this slowdown is actually caused by **muscle loss**, not just age. If you maintain muscle mass, you can keep your BMR high well into your 60s.
Metabolism Terms
NEAT
Non-Exercise Activity Thermogenesis. Energy burned by fidgeting, walking to the car, typing, and standing. This is often the difference between thin and overweight individuals.
TEF
Thermic Effect of Food. The energy required to digest, absorb, and dispose of ingested nutrients.
Adaptive Thermogenesis
A biological process where the body slows heat production (metabolism) to preserve energy during calorie restriction.
Resting Metabolic Rate (RMR)
Similar to BMR but less strict. BMR requires 8 hours sleep and fasting; RMR is looser. They are usually within 10% of each other.
About This Calculator
This BMR Calculator uses the Mifflin-St Jeor equation, widely recognized by the American Dietetic Association as the most accurate method for estimating basal metabolic rate in healthy individuals.